Research On Stress Field Distribution Of Hydraulic Fracturing Reservoir

The study of reservoir stress field distribution after hydraulic fracturing is a kind of technical method to calculate the stress field distribution of fractured reservoir with reservoir logging data and reservoir physical model.Study on the distribution of reservoir stress field after hydrolic fracture can be divided into hydrolic fracture effect evaluation and analysis of repeated fracturing.It can also provide the basis for the extension of the new artificial fracture.Nowadays,the research on the stress field distribution of the hydraulic fracturing reservoir often pays attention to the distribution of the stress field near the perforation point and the development trend of the artificial fracture.In view of this situation,this paper studied the effect of hydraulic fracturing on the reservoir rock mechanics parameters and optimized the porosity parameters,established the model of induced stress field around the wellbore and the model of fracture induced stress field.In this paper,the specific research content:(1)Combined with the principle of hydraulic fracturing,this paper analyzed the main factors affecting the mechanical properties of rock;the changes of the reservoir porosity,compressibility coefficient,elastic modulus and Poisson's ratio before and after fracturing,which provide the basis for subsequent fracturing reservoir calculation of stress field distribution.(2)As for The porosity of reservoir is easily affected by water injection and sand injection after conventional logging method for fracturing,this paper presents a new method to quantitatively calculate reservoir porosity after fracturing according to measurement results of reservoir porosity before fracturing and results of microseismic monitoring after fracturing.Firstly,the micro seismic monitoring results were analyzed,then extated the boundary of fracture and fracture profile according to the distribution characteristics of micro seismic events.At last calculated the the fracture volume and the porosity of fractured reservoir.Compared with porosity calculated by logging method,this method can effectively avoid the influence of water injection and sand injection.(3)Based on the basic steps of hydraulic fracturing,this paper made models of The in-situ stress field near the oil well,the stress field around the wellbore,theinduced stress field around the wellbore,the temperature induced stress field induced by the fracturing fluid,the stress field induced by the temperature change,and the fracture induced stress field around the wellbore.According to the superposition principle,this paper derived the formula for calculating the complex stress field around the wellbore after hydraulic fracturing.(4)The effectiveness of this method was verified with the field test of hydraulic fracturing micro seismic monitoring.The accuracy of reservoir induced stress field model is verified are analyzed by the calculation of fracture pressure.